Simple Timer for Xamarin Forms using Device Timer

While developing your application in Xamarin that requires a Timer, you have the option to use the Device Timer. However, one of the first caveat your would notice is that while Device Class has a Device.StartTimer method, it does not exposes a Stop method, leaving it to your own class to handle it.

I started by writing an interface for my proposed Timer Class ( in my case a Countdown timer), so that I could use it for mocking for the sake of my Unit Tests. This is how my interface looked like.